Paper feeding apparatus for image forming apparatus

ABSTRACT

A paper feeding apparatus for an image forming apparatus efficiently aligns the leading edge of a paper as being fed into the image forming apparatus regardless of the thickness of the paper. The paper feeding apparatus includes: first and second feeding roller assemblies rotatably installed on a paper feeding path and at least one tension idle wheel installed in anyone of the first and second feeding roller assemblies. The tension idle wheel is resiliently and elastically deformable in the radial direction thereof when the first and second feeding roller assemblies come into close contact with each other. A leading-edge alignment member is installed downstream of the first and second feeding roller assemblies to align the leading edge of a paper as being fed with respect to the apparatus.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.2005-91441, filed Sep. 29, 2005, in the Korean Intellectual PropertyOffice, the disclosure of which is hereby incorporated by reference inits entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus. Inparticular, the invention is directed to a paper feeding apparatus foran image forming apparatus.

2. Description of the Related Art

As shown in FIG. 1, a conventional image forming apparatus comprises apaper supply unit 1, a pickup unit 2 and a feeding unit 10, in which apaper P in the paper supply unit 1 is picked up by the pickup unit 2 andintroduced in the feeding unit 10. The paper P introduced in the feedingunit 10 and an image is formed on one surface thereof while it istransmitted through a developing unit 3 and a transfer unit 4. The imageformed on the paper is fixed as the paper passes a fixing unit 5, andthen the paper is outwardly discharged through a paper discharge unit 6.

Meanwhile, the feeding unit 10 has an alignment device for aligning theleading edge of the paper from the supply 1 in a straight line. FIG. 2shows a feeding unit 10 provided with an example of a leading-edgealignment device for the paper.

As shown in FIG. 2, the feeding unit 10 comprises a plurality of firstfeeding rollers 13 fitted on a driving shaft 12 and spaced from eachother. A motor 11 is connected to the driving shaft 12. A plurality ofsecond feeding rollers 15 are installed on an idle rotary shaft 14,which is spaced from the driving shaft 12, to confront with the firstfeeding rollers 13, and a leading-edge alignment shutter 16 for aligningthe leading edge of the paper.

The leading-edge alignment shutter 16 for the paper is installed in sucha way that when the leading edge of the paper P is aligned in a straightline, the leading-edge alignment shutter 16 rotates in the directionindicated by the arrow by the force from feeding the paper so as to opena paper feeding path under the influence of an elastic device.

In the above-mentioned paper feeding apparatus of a conventional imageforming apparatus, if the paper being fed is thick or the inertia of apicked-up paper is higher than the elastic force of the elastic memberfor elastically supporting the leading-edge alignment shutter 16 for thepaper, the leading-edge alignment shutter 16 may rotate and open thepaper feeding path before the leading edge of the paper is correctlyaligned. In such a case, the paper is misaligned when it is introducedinto the developing unit 3. Print errors and misaligned printing of animage on the paper can occur.

SUMMARY OF THE INVENTION

Accordingly, the present invention solves the above-mentioned problems.One object of the present invention is to provide a paper feedingapparatus for an image forming apparatus having an improved constructionso that the leading edge of a paper being fed into the image formingapparatus is always properly aligned regardless of the thickness of thepaper.

In order to achieve the above-mentioned objects, a paper feedingapparatus for an image forming apparatus, comprises: first and secondfeeding roller assemblies rotatably installed on a paper feeding path;at least one tension idle wheel positioned on one of the first andsecond feeding roller assemblies, the tension idle wheel beingelastically deformed in the radial direction thereof when the first andsecond feeding roller assemblies come into close contact with eachother; and a leading-edge alignment member installed downstream of thefirst and second feeding roller assemblies for aligning a leading edgeof a paper being fed to the invention.

According to a preferred embodiment of the present invention, thetension idle wheel slip-feeds the paper while the first and secondfeeding roller assemblies are spaced from each other. In addition, thepaper feeding apparatus may further comprise: a sensing unit having aplurality of sensors for sensing the leading edge of the paper; and adriving unit for rotationally driving the leading-edge alignment memberso as to open the paper feeding path and concurrently enabling the firstand second feeding roller assemblies to come into close contact witheach other when the sensing unit signals that the leading edge of thepaper is aligned.

The second feeding roller assembly may comprise a plurality of rollers,and a flexible rotary shaft for rotatably supporting the rollers andelastically deformed by an external force.

The tension idle wheel may be installed in the second feeding rollerassembly to be capable of idling.

In one embodiment, the tension idle wheel comprises: an outer rim whichcomes into contact with the first feeding roller assembly; an inner rimfitted on the rotary shaft of the second feeding roller assembly; and aplurality of spokes for connecting the outer rim to the inner rim, thespokes being convoluted in a predetermined angle in the radialdirection. The number of the spokes can be in the range of 2 to 5.Typically, the spokes are convoluted in a same direction.

In addition, it is preferable that the tension idle wheel be integrallyformed from resin, and that the outer rim has a smooth machined outersurface so that the paper slips over the outer rim.

The flexible rotary shaft may be formed from an optical fiber so that itcan also serve as a signal transmission path for the sensors.

In another embodiment, the leading-edge alignment member for the papermay comprise a blocking part positioned in the paper feeding path and anoperating part vertically depending from the blocking part. The paperfeeding apparatus may further comprise: a hinge for pivotally supportingthe leading-edge alignment member for the paper so that the blockingpart selectively opens the paper feeding path; and an elastic member forelastically supporting the paper's leading-edge alignment member, sothat the blocking part blocks the paper feeding path.

The elastic member may comprise a plurality of holders supported by therotary shaft of the second feeding roller assembly, and a plurality ofholders interposed between the respective holders and the operating partof the paper's leading-edge alignment member.

In addition, the driving unit may comprise: a cam member for selectivelycompressing an end of the operating part, so that the paper'sleading-edge alignment member is rotated in the direction for openingthe paper feeding path; and a motor for rotating the cam member, themotor being driven according to a signal from the sensing unit.

The elastic force of the flexible rotary shaft may be set to be lowerthan the force exerted by the compression coil springs, so that when thepaper's leading-edge alignment member rotates, the rotary shaft iselastically deformed, whereby the first and second feeding rollerassemblies come into close contact with each other.

Another aspect of the invention is to provide a method of aligning apaper in an image forming apparatus including the steps of: feeding apaper through a paper feed path of the apparatus into contact with amovable gate of a leading edge alignment member to align a leading edgeof the paper with the gate, sensing alignment of the leading edge of thepaper with the gate, and opening the gate in response to the sensedalignment and feeding the paper past the gate and through the paper feedpath.

These and other aspects of the invention will become apparent from thefollowing detailed description of the invention, which taken inconjunction with the annexed drawings, disclose various embodiments ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above aspects and features of the present invention will be moreapparent from the description for certain embodiments of the presentinvention taken with reference to the accompanying drawings, in which:

FIG. 1 is a view schematically showing the construction of aconventional image forming apparatus;

FIG. 2 is a perspective view showing a main part of a paper feedingapparatus employed in the image forming apparatus of FIG. 1;

FIG. 3 is a side elevational view of an image forming apparatusaccording to an embodiment of the present invention;

FIG. 4 is a front elevational view of FIG. 3;

FIG. 5 is a perspective view of a feeding roller assembly of a paperfeeding apparatus according to an embodiment of the present invention;

FIG. 6 is a perspective view of a tension idle wheel provided in thefeeding roller assembly of FIG. 5;

FIGS. 7A and 7B are top views for showing the alignment of a leadingedge of a paper for a paper feeding apparatus according to an embodimentof the present invention;

FIG. 8 is a side elevational view showing the feeding rollers in thefeeding roller assembly, which are engaged and rotated with each otheras shown in FIG. 3; and

FIG. 9 is a front elevational view of the apparatus of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinbelow, the preferred embodiments of the present invention aredescribed in detail with reference to accompanying drawings. In thefollowing description, a detailed description of known functions andconfigurations incorporated herein are omitted when it may make thesubject matter of the present invention rather unclear.

As shown in FIGS. 3 to 6, a paper feeding apparatus of an image formingapparatus according to an embodiment of the present invention includes afirst feeding roller assembly 110, a second feeding roller assembly 120,a plurality of tension idle wheels 200, a paper's leading-edge alignmentmember 300, a sensing unit 400, and a driving unit 500.

The first feeding roller assembly is rotatably installed on a paperfeeding path C. The first feeding roller assembly 110 includes a firstrotary shaft 111 and a plurality of first feeding rollers 112 mounted onthe rotary shaft 111 and spaced from each other. The first rotary shaft111 is connected with a drive source not shown in the drawings.

The second feeding roller assembly 120 is spaced from the first feedingroller assembly 110. The second feeding roller assembly 120 selectivelycomes into contact and rotates with the first feeding roller assembly110 to feed a paper P shown in FIG. 3. The second feeding rollerassembly 120 includes a second rotary shaft 121 and a plurality offeeding rollers 122 mounted on the second rotary shaft 121 and spacedfrom each other.

The second rotary shaft 121 is formed from a flexible material that iselastically deformable by an external force so that the first and secondfeeding roller assemblies 110 and 120 can selectively come into closecontact and rotate with each other as described later.

A plurality of the tension idle wheels 200 are installed on the secondfeeding rollers 120 and being capable of idling as shown in FIGS. 3 and5. When the first and second feeding roller assemblies 110 and 120 arespaced apart from each other, the tension idle wheels 200 come intocontact with the roller 112 as shown in FIG. 4 and rotate with the firstfeeding roller assembly 110, thereby slip-feeding a paper P. When thefirst and second roller assemblies 110 and 120 come into contact witheach other, the tension idle wheels 200 are elastically deformed in theradial direction thereof, whereby the close contact of the feedingroller assemblies 110 and 120 are not disturbed by the tension idlewheels 200. Although the drawing shows the tension idle wheels 200installed on the second feeding roller assembly 120 by way of anexample, the tension idle wheels 200 may be installed on the firstfeeding roller assembly 110.

Each of the above-mentioned tension idle wheels 200 comprises an outerrim 210, an inner hub or rim 220 and spokes 230, which are integrallyformed from a material such as resin. The outer rim 210 comes intocontact with a respective feeding roller 112 in the first feeding rollerassembly 110. The surface of the outer rim 210 is machined to be smoothso that it has a low frictional coefficient. In this manner, slippageoccurs when the outer rim 210 comes into contact with a paper P, therebyenabling the slip-feeding of the paper.

The inner rim 220 is fitted on and supported by the rotary shaft 121 ofthe second feeding roller assembly 120. The spokes 230 connect the outerrim 210 and the inner rim 220. As shown in FIG. 6, four spokes 230 areconvoluted in a same direction. The spokes 230 are shaped in this mannerso that the tension idle wheel 200 easily deforms when an external forceis applied to the tension idle wheel 200. However, the number of thespokes 230 is not limited to four, and it is sufficient if two or morespokes are provided.

The leading-edge alignment member 300 for the paper is installed toselectively open the paper feeding path downstream of the first andsecond feeding roller assemblies 110 and 120 as shown in FIG. 3. Theleading-edge alignment member 300 blocks the paper feeding path C, whenthe paper is fed slowly by the tension idle wheels 200 and the firstfeeding roller assembly 110 as slippage occurs between the paper P, thefirst feeding roller assembly 110 and the tension idle wheels 200, sothat the leading end of a paper comes into contact with the paper'sleading-edge alignment member, thereby evenly aligning the paper.

The leading-edge alignment member 300 for the paper comprises a gate orblocking part 310 and an operating part 320 in the form of an armvertically depending from the blocking part 310 shown in FIGS. 3 and 7A.A pivot hinge 330 pivotally supports the leading-edge alignment member300 so that the blocking part 310 selectively opens and closes the paperfeeding path C. In addition, spring assembly or elastic part 340resiliently engages the leading-edge alignment member 300 in such a waythat the blocking part 310 selectively blocks the paper feeding path C.As shown in FIGS. 7A, 7B and 8, the alignment member has a plurality ofarms that engage the springs of the elastic part 340 to bias thealignment member in a closed position. The operating arm shown in FIG.7A has a length greater than the arms engaging the springs.

The elastic part 340 is a spring assembly comprising a plurality ofholders 341 shown in FIGS. 3 and 8 supported by the rotary pivot shaft121 of the second feeding roller assembly 120, and a plurality ofcompression coils or springs 342 interposed between the holders 341 anda respective operating arm 320 of the leading edge alignment member 300.

A sensing unit 400 shown in FIG. 3 comprises a plurality of sensorsinstalled in parallel just before the blocking part 310 of theleading-edge alignment member 300 in order to sense whether theleading-edge of the paper P is properly aligned. In the presentembodiment, if the second flexible rotary shaft 121 is made from anoptical fiber, it is possible for the rotary shaft 121 also to serve asa signal transmission line without an additional signal transmissionpath for the sensors. The sensors 400 can be optical sensors, infraredsensors, or ultrasonic sensors. The sensor 400 detects the leading edgeof the paper P to determine the orientation of the paper on thealignment with respect to the apparatus to ensure that the printed imageis properly aligned on the paper.

If the sensing unit 400 signals that the leading edge of a paper isproperly aligned, a driving unit 500 rotationally drives the paper'sleading-edge alignment member 300 to open the paper feeding path C andconcurrently moves the first and second feeding roller assemblies 110and 120 into close contact with each other, so that the paper P with theproperly aligned leading edge is fed to the apparatus.

As shown in FIG. 3, the driving unit 500 includes a cam member 510 forselectively compressing an end of the operating arm 320 of theleading-edge alignment member 300, so that the leading-edge alignmentmember 300 is rotated in the direction for opening the paper feedingpath C. A motor 520 is connected to the cam member for rotating the cammember 510. The motor 520 is driven according to a signal from thesensing unit 400 which senses the aligned paper.

In addition, the elastic force of the second flexible rotary shaft 121is selected to be lower than that of the compression force of the coilsprings 342, so that when the leading edge alignment member 300 rotatesabout the pivot hinge 330, the rotary shaft 121 is elastically deformedas shown in FIG. 9, whereby the first and second feeding rollerassemblies 110 and 120 come into close contact with each other.

The alignment of a leading edge of the paper and the feeding of thepaper of the paper feeding apparatus configured as described aboveaccording to an embodiment of the present invention are now describedwith reference FIGS. 3, 4, 7A, 7B, 8 and 9.

FIGS. 3 and 4 are side and front elevational views showing the state inwhich the leading end of a paper P picked up by the apparatus andintroduced between the first and second feeding roller assemblies 110and 120, respectively. The first feeding roller assembly 110 and thesecond feeding roller assembly 120 are spaced from each other and thetension idle wheels 200 mounted on the second feeding roller assembly110 are in contact with the first feeding roller assembly 110.

The paper P introduced between the tension idle wheels 200 and the firstfeeding roller assembly 110 is fed by the feeding force exerted by thefirst feeding roller assembly 110. At this time, if the paper 110 is fedin the misaligned position as shown in FIG. 7A, one side P of theleading edge of the paper P first comes into contact with the blockingpart 310 of the paper's leading-edge alignment member 300. In thisposition, slippage occurs between the first feeding roller assembly 112,the paper P, and the tension idle wheels 200, whereby the other side P2of the leading edge of the paper P turns and comes into contact with theblocking part 310 since the one side P1 of the leading edge of the paperis stopped. As a result, the leading edge of the paper is evenly alignedwith the apparatus and the blocking part 310. The proper alignment ofthe leading edge of the paper is shown in FIG. 7B.

The completion of alignment of the leading edge of the paper as shown inFIG. 7B is sensed, for example, at the time all the sensors of thesensing unit 400 arranged in the widthwise direction of the paper areturned from “ON” to “OFF.” Then, after a predetermined length of timehas passed, the driving unit 500 is driven by a controller (not shown inthe drawing), so that the paper feeding path C is opened andconcurrently the first and second feeding roller assemblies 110 and 120are rotated while being in close contact with each other, to feed thepaper P with the leading edge.

Referring to FIGS. 8 and 9, as the motor 520 is driven, the cam member510 fitted on the shaft of the motor 520 rotates. As a result, thepaper's leading-edge alignment member 300 rotates clockwise about thehinge 330 shown in FIG. 8. Therefore, the end of the blocking part 310moves away from the paper feeding path C, whereby opening the paperfeeding path C. At the same time, as the operating part 320 compressesthe compression coil springs 342 of the elastic part 340, the secondrotary shaft 121 is elastically deformed so that the second feedingroller assembly 120 comes into close contact with the first feedingroller assembly 110. At this time, the tension idle wheels 200 mountedon the second feeding roller assembly 120 are radially deformed, so thatthey do not prevent the first and second feeding rollers 112 and 122from coming into close contact with each other.

The paper P is then fed along the opened paper feeding path C, and whenthe tail end of the paper being fed passes the plurality of sensors, themotor 520 is driven in a reverse direction, thereby returning theleading-edge alignment member 300 and the second feeding roller assembly120 to their original positions.

As described above, according to the present invention, the alignment ofthe leading edge of a paper being fed is performed not by using theforce for feeding the paper but by opening a paper feeding path afteraligning the leading edge of the paper while slippage occurs in thepaper when the paper feeding path is blocked. Therefore, the leadingedge of the paper can be efficiently aligned regardless of the thicknessof the paper. In addition, according to the present invention, becausethe alignment of the leading-edge of a paper can be smoothly performedeven if the paper is thick, it is possible to reduce the occurrence ofprint error caused by the serpentine feeding of a paper.

Although representative embodiments of the present invention have beenshown and described in order to exemplify the principle of the presentinvention, the present invention is not limited to the specificembodiments. It will be understood that various modifications andchanges can be made by one skilled in the art without departing from thespirit and scope of the invention as defined by the appended claims.Therefore, it shall be considered that such modifications, changes andequivalents thereof are all included within the scope of the presentinvention.

1. A paper feeding apparatus for an image forming apparatus, comprising:first and second feeding roller assemblies rotatably mounted in a paperfeeding path; at least one tension idle wheel mounted on either thefirst and second feeding roller assemblies, the tension idle wheel beingresiliently deformable in a radial direction thereof when the first andsecond feeding roller assemblies come into close contact with eachother; and a leading-edge alignment member positioned downstream of thefirst and second feeding roller assemblies to align the leading edge ofa paper as being fed through the feeding path.
 2. A paper feedingapparatus as claimed in claim 1, wherein the tension idle wheelslip-feeds the paper when the first and second feeding roller assembliesare spaced apart from each other.
 3. A paper feeding apparatus asclaimed in claim 1, further comprising: a sensing unit having aplurality of sensors for sensing alignment of a leading edge of thepaper with respect to the apparatus; and a driving unit for rotationallydriving the leading-edge alignment member to open the paper feeding pathand concurrently causing the first and second feeding roller assembliesto come into close contact with each other when the sensing unit sensesthat the leading edge of the paper is in a predetermined alignment withrespect to the apparatus.
 4. A paper feeding apparatus as claimed inclaim 3, wherein the second feeding roller assembly comprises: aplurality of rollers; and a flexible rotary shaft for rotatablysupporting the rollers, wherein the rotary shaft can be elasticallydeformed by an external force.
 5. A paper feeding apparatus as claimedin claim 3, wherein the tension idle wheel is installed in the secondfeeding roller assembly to be capable of idling.
 6. A paper feedingapparatus as claimed in claim 5, wherein the tension idle wheelcomprises: an outer rim which comes into close contact with the firstfeeding roller assembly; an inner hub mounted on the rotary shaft of thesecond feeding roller assembly; and a plurality of spokes connecting theouter rim and the inner rim, the spokes being convoluted in apredetermined angle in the radial direction.
 7. A paper feedingapparatus as claimed in claim 6, wherein the tension idle wheel includes2 to 5 spokes convoluted in a same direction.
 8. A paper feedingapparatus as claimed in claim 7, wherein the tension idle wheel isintegrally formed from a resin.
 9. A paper feeding apparatus as claimedin claim 8, wherein the outer rim has a smooth machined outer surface sothat slippage occurs between a paper and the outer surface of the rim.10. A paper feeding apparatus as claimed in claim 4, wherein theflexible rotary shaft is formed from an optical fiber and is coupled tothe sensors to function as a signal transmission path for the sensors.11. A paper feeding apparatus as claimed in claim 4, wherein theleading-edge alignment member comprises a blocking part positioned inthe paper feeding path and an operating arm vertically depending fromthe blocking part, and wherein the paper feeding apparatus furthercomprises: a hinge for pivotally supporting the leading-edge alignmentmember so that the blocking part selectively opens and closes the paperfeeding path; and a spring member for biasing the leading-edge alignmentmember to the closed position to block the paper feeding path.
 12. Apaper feeding apparatus as claimed in claim 11, wherein the springmember comprises: a plurality of spring holders supported by the rotaryshaft of the second feeding roller assembly; and a plurality of springspositioned between the respective holders and respective operating armsof the leading-edge alignment member.
 13. A paper feeding apparatus asclaimed in claim 12, wherein the leading edge alignment member includesan operating arm, and where the driving unit comprises: a cam member forselectively compressing an end of the operating arm, so that theleading-edge alignment member rotates in the direction to open the paperfeeding path; and a motor for rotating the cam member, the motor beingdriven according to a signal from the sensing unit.
 14. A paper feedingapparatus as claimed in claim 13, wherein the resilience and flexibilityof the flexible rotary shaft is weaker than a force exerted by thecompression coil springs, so that when the leading-edge alignment memberrotates, the rotary shaft is resiliently deformed, whereby the first andsecond feeding roller assemblies come into close contact with eachother.
 15. An image forming apparatus comprising: first and secondfeeding roller assemblies rotatably mounted in a paper feeding path ofthe apparatus; at least one tension idle wheel mounted on one of thefirst and second feeding roller assemblies, the tension idle wheelcoming into close contact and rotating with the corresponding feedingroller assembly to slip-feed a paper through the paper feeding path whenthe first and second feeding roller assemblies are spaced apart fromeach other, and where the tension idle wheel is resiliently deformablein the radial direction thereof when the first and second feeding rollerassemblies come into close contact with each other; a leading edgealignment member for the paper positioned to selectively open and closethe paper feeding path downstream of the first and second feeding rollerassemblies, the leading-edge alignment member aligning a leading edge ofthe paper being slip-fed by the tension idle wheel when the leading-edgealignment member is in a closed position blocking the paper feedingpath; a sensing unit having a plurality of sensors for sensing alignmentof the leading edge of the paper with respect to the apparatus; and adriving unit for rotationally driving the leading-edge alignment memberto open the paper feeding path when the sensing unit senses apredetermined alignment of the paper and concurrently causing the firstand second feeding roller assemblies to come into close contact witheach other to feed the paper through the paper feeding path of theapparatus.
 16. The image forming apparatus of claim 15, wherein thefirst feeding roller assembly includes a first roller, the secondfeeding roller assembly includes a second roller, and the first rollerassembly is movable from a first position where the tension idle wheelcontacts the second roller and the first roller is spaced from thesecond roller, and a second position where the first roller contacts thesecond roller to feed the paper through the paper feeding path.
 17. Theimage forming apparatus of claim 16, wherein the at least one tensionwheel and the first roller are rotatably mounted on a flexible shaft.18. The image forming apparatus of claim 17, wherein the at least onetension wheel has a diameter greater than a diameter of the firstroller.
 19. The image forming apparatus of claim 16, wherein theleading-edge alignment member includes a movable gate member to closeand block the paper feeding member, and wherein the first and secondfeed roller assemblies feed the paper to contact the gate member toalign the paper with an edge of the gate member.
 20. A method ofaligning a paper in an image forming apparatus, the method comprising:feeding a paper through a paper feed path of the apparatus into contactwith a movable gate of a leading edge alignment member to align aleading edge of the paper with the gate, sensing alignment of theleading edge of the paper with the gate, and opening the gate inresponse to the sensed alignment and feeding the paper past the gate andthrough the paper feed path.
 21. The method of claim 20, wherein theapparatus includes a first feed roller having a first roller and atension idle wheel, and a second feed roller having a second roller, thetension idle wheel having a diameter greater than a diameter of thefirst roller and being resiliently deformable, the method comprising:contacting the idle wheel with the second roller in a first position tofeed the paper through the paper feed path into contact with the movablegate, and simultaneously opening the gate and moving the first feedroller to a second position in response to the first feed roller to asecond position in response to the sensed alignment of the paper,wherein the first feed roller contacts the second roller an the idlewheel is deformed when the first feed roller is in the second position.